It would be impractical for the US to monitor how its border guards use the massive databases it is building on European citizens, US Homeland Security Security secretary Michael Chertoff told the European Parliament yesterday.

Answering questions before an extraordinary meeting of the European Parliament's Committee on Civil Liberties, Justice and Home Affairs, Chertoff defended the Automated Targeting System - a US database that creates profiles of people who cross America's borders.

MEPs questioned Chertoff on the US collection of Passenger Name Records, which was the precursor to the Automated Targeting System.

Dutch MEP Sophie Int-Veld told Chertoff: "It's never justified to give unlimited and uncontrolled powers to any government." She is the rapporteur for the Parliament on the EU's attempt to restrain the US collection of data about European citizens.

She asked for more evidence of the results the US is getting from its "massive collection of data" in the hunt for terrorists.

Chertoff provided two anecdotal examples and presented another six to the Parliament. But, he said the decisions of border guards to detain or bar people entering the US could not be scrutinised.

"We don't catalogue every single instance in terms of keeping a statistical database of each time these measures make us safer, partly because the information that is obtained is usually one of a number of factors that enter into the decision of a border inspector to talk to people," he told the Parliament.

"We don't always capture with precision when the border inspector has relied upon that. I don't know whether it would be possible to construct a system in practical terms that would do that."

He was asked to consider the oft-repeated criticism of the US "war on terror", that it was being fought at the expense of the fundamental rights of the citizens it claims to protect.

In answer, Chertoff cited the doubts of British Home Secretary John Reid about the efficacy of European legal traditions in the face of terrorism.

"There's one very big difference between prosecuting a crime that has occured in the past and to seek justice," said Chertoff.

He suggested the Anglo-Saxon legal principle that "it is better that a thousand guilty go unpunished lest one innocent man be wrongly punished" might be outmoded.

"The balance becomes somewhat different when we aim to prevent attacks," he said. "You must ask yourself this question - whether you would be satisfied to be constrained by slow-moving processes if the consequence would be to allow an attack go forward that would kill thousands of people or perhaps millions of people, including ones own children."

He told a press conference later that legal traditions enshrined in criminal law and laws governing war might not "adequately reflect" the 21st century threat, "where we have non-state networks capable of waging war as effectively and destructively as nation states could a century ago".

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